The present invention relates to a mechanical encoder with a plurality of mutually drivingly connected value embodying carriers with encoding step markings. The encoding step markings of the value embodying carriers contact sensing apparatus for the production of output signals corresponding to the position of the value embodying carriers. A multiple digit mechanical encoder, in which information can be directly read out and/or employed for subsequently driven apparatus, has an input shaft, which for example, is directly connected with a shaft, the rotary position of which is to be determined or monitored, or is connected through a drive with a corresponding shaft or else is connected with a suitable measuring value transducer, which transduces rotary position to a control quantity. The output data of this type of encoder is either a visually readable number and/or a signal represented in a code, which in this form is directly used for control or regulation or else is retransmitted to data processing apparatus.
This type of encoder is used mainly for the measurement of an angle of rotation, an angular position or also a linear displacement, for example, when a rack is arranged in engagement with a pinion.
Conventionally with such encoders the individual value embodying carriers are so coupled with each other, for example, through altered tooth wheels, that after each full revolution of a value embodying carrier, the next higher value, value embodying carrier is respectively further driven a step. However, at present with the direct indication of the encoded results, in particular when the rotary position of the value embodying carriers is read out through contacts, through photoelectrical or magnetic means, so that this data in the form of an electrical signal may be transmitted to data processing apparatus, difficulties result in that during the stepping action, that is during the commutation from one position of the value embodying carrier to the next, an indefinite intermediate condition is passed through. In particular, with multidigit encoders the unavoidable mechanical play between the individual value embodying carriers leads to non-simultaneous switching, or forward movement of the individual value embodying carriers.
With a decimal encoder can, for example, during the transition from 0999 to 1000 also the numbers 0990, 0900, and 0000 be read out and transmitted in the form of electrical signals. With direct indication of numbers, these errors can possibly be corrected; by the indication through electrical, optical, or magnetic devices, is however, error information transmitted to the data processing apparatus. Assume for example, that an apparatus is to be brought to position, which corresponds to the number 1000. In order to save time, the apparatus should be brought, for example, with high speed to the position 0997 and the last three steps should occur, with proportionately slower speed. At this point, after the position 0997 has been obtained, a correspondingly slower transport speed is shifted to; however, with the commutation from 0999 to the number 1000 the intermediate position 0990 is passed through, so the control system could take this as an occurrence to restore the apparatus to acceleration, as noted above, to move the instrument with higher speed to the position 0997. It is evident that known mechanical encoders are not suitable for acceptable control of the referred to equipment.